A clamping device of this kind is known from DE-U-81 14 063. The known clamping device comprises a hollow cylindrical wall-mounted holder part, in which a solid cylindrical operating holder part can slide to and fro. A spring is accommodated between the two holder parts. The spring is supported on one side on the bottom of the hollow cylindrical wall-mounted holder part and on the other side in a recess which is formed in the solid cylindrical operating holder part. Furthermore, the operating holder part is provided with a locking finger which extends downwards and is intended to engage in locking projections arranged on the bottom of the wall-mounted holder part. The connection between the locking finger and the locking projections is such that limited movement between the two holder parts is possible. The hollow cylindrical wall-mounted holder part is provided with a slot-shaped insertion opening, while the solid cylindrical operating holder part is provided with a slot-shaped recess. By pressing the operating holder part inwards into the wall-mounted holder part, counter to the spring force, the insertion opening and the recess will move into line with one another. At that moment, part of a somewhat flexible product can be inserted. If the operating holder part is then pressed outwards again by the spring loading, that part of the product which has been inserted will be clamped between the edges of the insertion opening in the wall-mounted holder part and the edges of the recess in the operating holder part.
A drawback of this known clamping device is that the operating holder part is of substantially solid design and therefore does not have a uniform wall thickness corresponding to the wall thickness of the wall-mounted holder part. This entails high production costs and often the need to use different materials for the holder parts. Furthermore, the solid operating holder part lies inside the hollow wall-mounted holder part. Each time it is used, dirt from the hand of a user can as a result pass between the two holder parts. The accumulated dirt source produced in this way causes unhygienic conditions, which is undesirable when the clamping device is used for towels and the like. Furthermore, the dirt which penetrates between the two holder parts may have the result that the clamping device can no longer operate effectively, for example because the holder parts can only be moved with great difficulty with respect to one another.